DK200200567A - Process and plant for evaporative concentration and crystallization of a viscous lactose-containing aqueous liquid - Google Patents

Description

PATENT CLAIMS 1. A process for evaporative concentration and crystallization of a viscous lactose-containing aqueous liquid, comprising: (a) introducing the lactose-containing aqueous liquid having a dry solids content of 40-75% by weight into a zone and therein subjecting it to the following simultaneous measures .- (i) progressive heating at a temperature above 40 °C but below the maximum temperature for crystallization of α-lactose monohydrate from the liquid; (ii) removal of vapour evaporated from the liquid; and (iii) mechanical agitation able to provide a crystallization promoting decrease of the viscosity of the liquid with crystals formed and suspended therein; to progressively concentrate and simultaneously crystallize the agitated liquid, and (b) recovering the resulting slurry from said zone at a total solids content above 75% for cooling and optional disintegration and further drying. 2 . The process of claim 1 performed as a continuous operation, wherein said lactose-containing aqueous liquid is introduced into one end of an elongated essentially horizontal zone; the heating in measure (i) is carried out by supplying a heating medium to a jacket surrounding at least a portion of said zone; said vapour evaporated from the liquid is in measure (ii) removed by purging said zone by passing an air flow therethrough; the agitation in measure (iii) is performed by rotating an essentially horizontal shaft carrying agitation means to agitate the total volume of liquid present in said zone; and recovering said slurry from the end of the elongated zone opposite to said one end. 3. The process of anyone of claims 1 or 2, wherein said lactose-containing aqueous liquid used as starting material is selected from the group consisting of concentrates of permeate formed by ultra filtration of sweet or acid whey or milk, concentrates of whey or of demineralized whey, and mother-liquor from lactose recovery, and lactose slush. 4. The process of anyone of claims 1 or 2, wherein the heating in measure (i) is caused to increase the temperature of the liquid to 50-90°C. 5. The process of claim 1, wherein the removal of vapour in step (ii) is accomplished by maintaining a reduced pressure in said zone. 6. The process of anyone of claims 1 or 2, wherein the agitation of measure (iii) is performed at an intensity to provide a shear rate of 200-3,500 s'1 in the liquid. 7. The process of anyone of claims 1 or 2, wherein the agitation of measure (iii) is performed at an intensity to provide a shear rate of 300-3,000 s'1 in the liquid. 8. The process of anyone of claims 1 or 2, wherein the agitation of measure (iii) is performed at an intensity to provide a shear rate of 400-2,500 s"1 in the liquid. 9. The process of claim 1 or 2, wherein said cooling and optional disintegration and further drying comprise passing said slurry through an auger apparatus having cooling surfaces and subsequently through a disintegrating and drying device. 10. A plant for converting an aqueous lactose-containing liquid into free-flowing particles comprising (a) a first device having (i) an elongated cylindrical horizontal housing of essentially circular vertical cross-section, (ii) an inlet for lactose- containing liquid at one end of said housing, (iii) a rotatable horizontal shaft axially in said housing, (iv) paddles radially extending from the shaft towards the cylindrical wall of the housing, (v) a heating jacket surrounding at least partially said housing, (vi) openings at each end of the housing for removing vapours and, (vii) an outlet in the housing for lactose-containing gruel near the end opposite to said one end, (b) a cooling device connected to said outlet, and (c) a disintegrating and drying device connected to said cooling device. 11. The plant of claim 10, wherein the paddles (iv) are spaced and mutually displaced on said shaft and have such dimensions that the main area of the inner wall of the housing surrounded by the heating jacket (v) is periodically passed by a paddle tip at a distance of 5-25 mm. 12. The plant of claim 10, wherein the cooling device (b) is designed as an auger having at least one screw and being provided with a jacket and/or hollow screw shaft(s) for receiving a cooling medium. 13. The plant of claim 10, wherein the disintegrating and drying device is selected from a stirred fluidized bed and a tumbling drying drum.